1. Field of the Invention
The present invention relates both to a device and to a method for changing the noise characteristic in a receiver of a data transmission system.
Devices and methods for improving the noise characteristic in receivers are known which use either a noise predictor or a noise attenuator. With the same number of coefficients, a better signal/noise ratio can be obtained with the noise attenuator than with the noise predictor. Because of the feedback structure, the coefficients have to be continuously monitored with respect to stability. This is very complex and also does not always lead to the desired success.
From Published, European Patent Application EP 0 707 401 A2, a device is known which exhibits a noise predictor.
It is accordingly an object of the invention to provide a device and a method for changing the noise characteristics in a receiver that overcome the above-mentioned disadvantages of the prior art devices and methods of this general type, which provides for a greater or better signal/noise ratio, respectively, and is technically simple to implement.
With the foregoing and other objects in view there is provided, in a data transmission system having a receiver, a device for changing a noise characteristic in the receiver. The device includes a noise predictor having coefficients that can be adaptively adjusted to a respective interference; and a noise attenuator connected to the noise predictor and has fixed dimensions.
According to the invention, the object is achieved by the device for changing the noise characteristic in the receiver of a data transmission system. The device contains the noise predictor that is connected to the noise attenuator, wherein the dimensioning of the noise attenuator is fixed and coefficients of the noise predictor can be adaptively adjusted to the respective interference.
With the foregoing and other objects in view there is further provided, in accordance with the invention, a method for changing noise characteristics in a receiver. The method includes the steps of providing a data transmission system having the receiver, a noise predictor, and a noise attenuator; fixing a dimensioning of the noise attenuator; and adaptively adjusting coefficients of the noise predictor to a respective interference.
According to a preferred embodiment of the invention, the fixed noise attenuator is a first-order system having the following transfer function             NA      ⁡              (        z        )              =                            a          1                +                              a            2                    ·                      z                          -              1                                                  1        +                              b            2                    ·                      z                          -              1                                            ,
where ai and bi are the coefficients of the noise attenuator. For reasons of stability, |b2|xe2x89xa61 initially. In contrast, z describes the complex z domain operator (z transformation). By definition, the following holds true:
Z=ej2xcfx80f/fa,
where fa is the sampling frequency of the time-discrete system.
According to another preferred embodiment, the adaptive noise predictor is a first-order system having the following transfer function:
NP(z)=c1+c2xc2x7zxe2x88x921.
The noise attenuator is preferably connected with feedback in order to achieve the required signal/noise ratios.
Although a multiplicity of fixed coefficients is possible for the noise attenuator, the following have been found to be particularly advantageous at least in approximation:
a1=xe2x88x92xe2x85x9e; a2=0; b2=0
or
a1=xe2x88x922; a2={fraction (9/16)}; b2=xc2xd.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a device and a method for changing the noise characteristic in a receiver of a data transmission system, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.